1. Field of the Invention
This invention relates in general to a method of plumbing installation during rough construction which allows all of the in-wall plumbing to be installed during rough and more specifically involves a cap for sealing the open ends of trap adapters and other externally threaded pipes to conduct the pressure test and to protect the threads.
2. Description of the Related Art
During the rough construction of a building, such as an apartment building, the main plumbing lines are installed within the framework before the wall covering boards are attached. In this manner, the plumbing systems can be immediately tested for visible leaks which can then be repaired before the pipe connections are hidden from view by the wall covering boards.
In the drain system, typically, vertical pipes made of two-inch diameter cast iron are disposed in the framework. These pipes are placed end-to-end and are joined with a coupling band. The coupling band is tightened with a hose clamp.
T-shaped side connections (tap-T's) are installed at intersections in the cast iron pipes for the connection of sinks or the like. In an apartment building or similar structure, there may be hundreds of tap-T's. The tap-T outlet to the sink is internally threaded with pipe threads. For pressure test, all of these tap-T's openings must be sealed. A head typically of ten feet of water is applied to the pipes, usually by filling the vertical drain pipe at a high location with water from a hose. The system is then visually inspected for leaks, and, if required, is repaired and is tested again.
Conventionally, several methods are used to seal the tap-T's for test. A common method involves the use of "test nipples". Test nipples are iron pipes, typically of six or twelve inches in length. One end is permanently capped, such as with a pipe cap with sealant on the threads. The open end, externally threaded with pipe threads, is connected to the open end of the tap-T. A sealant, such as teflon tape or pipe dope, must be used to seal the threads and prevent leaks. Large pipe wrenches are required to attach the test nipples to assure no leaks around the threads. After test, the test nipples are removed, which again requires the use of large pipe wrenches.
One disadvantage of the test nipple approach is that a large number of heavy, iron nipples must be moved around. Another disadvantage is that the persons making the rough installation and test must have and must carry large pipe wrenches and pipe thread sealant which they otherwise would not.
In another method, an extension pipe or a trap adapter is attached to the tap-T, and an expansion plug, commonly called a "dollar plug" is inserted in the end of the pipe. The dollar plug seals against the inside surface of the pipe. An expansion plug of this type is disclosed in U.S. Pat. No. 2,993,616 of W. A. Carlile, Jr. et al titled "Expansible Closure". There are a number of disadvantages to the use of expansion plugs. Often, they are expelled from the pipe under pressure test. This is sometimes caused by expansion of the pipe after the plug is installed. To prevent expulsion of dollar plugs, persons installing the plugs often resort to tying the plugs in place with wire over the end of the pipe. Of course, this is labor consuming. Another disadvantage of dollar plugs is that they provide no protection for the external threads of the trap adapter during further construction.